Device for controlling the injection of fuel in internal combustion engines

ABSTRACT

For a fuel control system of an internal combustion engine having a needle which lifts to admit fuel, an electromagnetic means is provided for lifting the needle which electromagnetic means is energized through discharging of a condenser, the condenser being charged through an alternator operated by the engine. The circuit connecting the alternator to the condenser and to the electromagnetic winding comprises means to cause the condenser to discharge and may also include means to change the time the needle is held in lifted position and to vary the magnetizing current.

United States Patent [191 J aulmes DEVICE FOR CONTROLLING THE INJECTION OF FUEL IN INTERNAL COMBUSTION ENGINES Eric Jaulmes, Paris, France Ateligers De La Motobecane, Pantin (Seine Saint Denis), France Filed: May 10, 1972 Appl. No.: 252,073

[75] Inventor:

[73] Assignee:

[30] Foreign Application Priority Data May 12, 1971 France 71.17094 U.S. Cl. 123/32 EA, 123/32 AE Int. Cl. F02b 3/00 Field of Search 123/32 EA References Cited UNITED STATES PATENTS 2/1962 Pickens v 123/32 EA 11/1964 Deneen 123/32 EA 11/1968 Reyner 123/32 EA 3/1969 Bassot 123/32 EA June 11, 1974 3,490,425 l/1970 Bassot 123/32 EA 3,565,048 2/1971 Monpetit 123/32 EA 3,613,644 10/1971 Porsche 123/32 EA 3,659,563 5/1972 Monpetit 123/32 EA 3.665901 5/1972 Monpetit 123/32 EA 3,710,763 l/1973 Bassot 123/32 EA Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney, Agent, or Firm-Greene & Durr [57] ABSTRACT For a fuel control system of an internal combustion engine having a needle which lifts to admit fuel, an electromagnetic means is provided for lifting the needle which electromagnetic means is energized through discharging of a condenser, the condenser being charged through an alternator operated by the engine. The circuit connecting the alternator to the condenser and to the electromagnetic winding comprises means to cause the condenser to discharge and may also include means to change the time the needle is held in lifted position and to vary the magnetizing current.

1 Claim, 9 Drawing Figures PATENTEmun 1 1 1924 3.815556 sum 1 or 2 PATENTEDJUN 1 1 I974 3.815556 sum 2 a; 2

FlG.6 FIG. 7

FIG.8' FlG.9

DEVICE FOR CONTROLLING THE INJECTION OF FUEL IN INTERNAL COMBUSTION ENGINES The present invention relates to improvements in the control of injectors used for the" fuel supply of reciprocating internal combustion engines.

In certain forms of construction of these injectors, the needle of the injector is controlled by passing a low voltage direct current, for a controlled period of time, through the winding of an electromagnet, the armature of which is connected to this needle.

The control of period can be achieved by electronic means, using transistors, which are appropriate where one has a source of DC voltage, such as the battery of an automobile vehicle, for example.

When this source of current does not exist on a vehicle, one generally finds an alternator, the frequency of which is proportional to the speed of rotation of the engine.

The invention consists essentially in an electric circuit including a condenser, connections for charging the condenser, an electromagnetic winding arranged so that the needle is lifted when current flows in the winding, means for causing discharge of the condenser through the winding in synchronism with the cycles of the engine, and means for varying the discharge to thereby vary the period of each lift of the needle.

Preferably the control of the period of the lift of the needle is carried out by a modification of the characteristics of the discharge circuit of the condenser, consisting in varying the sustaining current in the winding produced by a discharge.

Such an arrangement permits a very precise regulation of the fuel supply, by inserting at will different parameters in the circuit, with a view to modifying the lifting time of the needle.

The accompanying drawings show several examples of the electric circuits of fuel control systems embodying this invention. In these drawings:

FIG. I shows a simple circuit;

FIG. 2 shows the same circuit modified by the insertion of a diode in the discharge circuit of the con denser;

FIGS. 3, 4 and 5 show three further variations;

FIGS. 6 to 9 show readings on an oscilloscope, reproduced by way of explanation.

In FIG. 1, a condenser C is charged by a winding L of an alternator, through a diode D and the discharge of this condenser in a winding 1 of a controlling electromagnet for a needle of an injector is brought about by the triggering of a thyristor T, by a control pulse generated at the correct moment in each cycle of the engine by known means, not shown. This discharge causes changes in the voltage at X (FIG. 3), as illustrated by the curve in FIG. 6, and creates in the winding 1 a magnetizing current which rises to a large instantaneous value, as illustrated by the curve of FIG. 7, this current giving rise to an attraction force F on its core, to which is connected the needle of the injector, not shown. But FIG. 7 shows also that this magnetizing current decreases rapidly, to attain very quickly a value close to zero.

If the circuit of FIG. 1 is augmented by a diode D connected in parallel with the winding 1, as shown in FIG. 2, one finds that the discharge of the condenser C changes form (see FIG. 8) and that the magnetizing current, as shown in FIG. 9, retains an appreciable value during a relatively long time, this current remaining sufficient to maintain the needle of the injector lifted.

A comparison between FIGS. 7 and 9 will clearly bring out the difference between the results obtained by thearrangement without the diode D (FIG. 7) and the arrangement including the diode D (FIG. 9). In these two Figures, the shaded zone represents the energy of the magnetizing current. It appears clearly that this energy in FIG. 7 is less than in FIG. 9.

If one connects in series with the diode D, a variable resistance, one will be able to obtain a continuous variation of the magnetizing current between the extreme values illustrated by the curves of FIGS. 7 and 9 and, in consequence, a lesser or greater period of lift for the needle of the injector. One thus creates the possibility of varying the fuel supply to the engine by electronic means which are very simple and of tested reliability.

The winding is excited by an impulse of damped nonperiodic form. This type of capacitative discharge permits one to have available the maximum energy in the shortest time for the purpose of control of the needle of the injector.

One creates control pulses of a particular wave form which it is possible to modify, in its negative part, by means of the insertion in the discharge circuit of a diode and of a variable resistance mounted in series, or of a thyristor.

As shown in FIG. 3, one can, for example, use a potentiometer P. When the latter is at zero, one is back at the case of FIG. 2, and the opening time of the needle is maximum, while if this potentiometer P is at its maximum value, one is back at the case of FIG. 1, with a minimum time of opening. By utilizing well-known means, the resistance of this potentiometer P can be caused to vary as a function of the intake suction of the engine, of the temperature, or of the position of the accelerator, for example.

FIG. 4 shows another variation, including a thyristor Th to adjust the time of lift of the needle. In this case, a synchronization signal is taken from the alternator L, through the diode d. This signal feeds directly a dephasing circuit Cd constituted by a unijunction transistor UJT, a potentiometer P (or any other device producing an automatic adjustment as a function of external parameters) a condenser c and two resistances R and R FIG. 5 shows another variation, according to which the regulation is carried out by acting on the charging voltage of the condenser C. This adjustment is carried out by a short-circuiting to a greater or less extent of the winding L of the alternator. It is sufficient for this purpose to arrange a thyristor Ta in parallel with L and to control the latter v by a dephasing circuit Cd synchronized with the alternator, of known type and analogous to the dephasing circuit of FIG. 4. One can thus vary the charging voltage of the condenser C between zero and the maximum value.

It will be realized that the invention is particularly of interest in the case of two-stroke engines since, for these engines, the problem arises in different terms than those in which it arises for four-stroke engines. In the latter, in fact, it is possible to make some injection indirectly, that is to say some injection in the inlet passage upstream of the inlet valve, and one has available for this all the time during which the inlet valve is 6155621761513 to say 5565i "i /zrevaiiitiansar the engine. In contrast, in two-stroke engines, on the one hand it is necessary to make some injection at each revolution of the engine, and on the other hand, if one made this injection into the inlet passage, since the gases admitted into the crankcase serve for scavenging of the cylinder, one would lose some of the fresh gas by exhaust. It is thus of interest to be able to make some injection directly into the cylinder, after scavenging, that is to say after the closure of the exhaust. The scavenging will then be carried out by fresh air, and the injection will take place after this scavenging, during the rising of the piston, during'the very short time which separates the moment when the piston passes the top of the exhaust port and the moment of firing, which is evidently situated before the top dead center.

I claim:

1. In a device for controlling the feeding of fuel to an internal combustion engine comprising an injector having a needle which lifts to inject the fuel and an electronic circuit comprising a condenser, connections for charging the condenser with a charging impulse, an electromagnetic winding arranged so that the needle is lifted when current flows in the winding and means to trigger the discharge of the condenser into the winding in synchronism with the cycles of the engine, the improvement wherein said latter means to trigger the discharge of the condenser comprises a thyristor and also comprising control circuit means to vary the sustaining current for lifting the needle, said control circuit having a second thyristor connected in parallel with said winding and comprising means including a unijunction transistor for controlling the second thyristor in proportion to the charging impulse for charging the condenser. 

1. In a device for controlling the feeding of fuel to an internal combustion engine comprising an injector having a needle which lifts to inject the fuel and an electronic circuit comprising a condenser, connections for charging the condenser with a charging impulse, an electromagnetic winding arranged so that the needle is lifted when current flows in the winding and means to trigger the discharge of the condenser into the winding in synchronism with the cycles of the engine, the improvement wherein said latter means to trigger the discharge of the condenser comprises a thyristor and also comprising control circuit means to vary the sustaining current for lifting the needle, said control circuit having a second thyristor connected in parallel with said winding and comprising means including a unijunction transistor for controlling the second thyristor in proportion to the charging impulse for charging the condenser. 